1. Technical Field
The present invention relates to apparatuses and methods for indicating failure or satisfaction of a parameter of a fluid that is transferred through a conduit.
2. Description of the Related Art
Many people use breathing therapy, such as oxygen therapy, for various ailments such as asthma, emphysema, chronic bronchitis, occupational lung disease, lung cancer, cystic fibrosis and congestive heart failure. Many such diseases are chronic in nature and require long-term treatment regimens. Home-based oxygen therapy permits these individuals to lead active, productive lives by letting them receive oxygen therapy at home instead of in a hospital or doctor's office.
Home-based oxygen therapy is certainly liberating to those who require it. However, it presents a host of problems. First, a physician typically writes a prescription for oxygen therapy. The prescription dictates the flow rate in terms of liters of oxygen per minute (LPM or L/M) and how often the breathing treatment should be administered. Furthermore, sometimes the oxygen therapy must be administered while exercising, sleeping or sometimes continuously. A problem arises in that complicated equipment may be needed. Small liquid crystal displays or hard-to-read mechanical gauges are needed to display, for example, flow rate. Reading such devices while exercising or while reclining in a darkened room can be difficult. Furthermore, many patients may be elderly and may have failing eyesight. For this group of patients, reading parameters, such as the flow rate, is especially difficult. Therefore, an easier method for determining characteristics of a fluid, such as flow rate, is needed.
Before describing the potential solutions to this problem, further background regarding breathing treatments will be addressed. For instance, there are three common tools used for providing oxygen therapy: compressed gas, liquid gas or an oxygen concentrator.
First, with compressed gas, oxygen is stored, under pressure, in a cylinder equipped with a regulator that controls the flow rate. Because the flow of oxygen out of the cylinder is constant, an oxygen-conserving device may be attached to the system to avoid waste. This device releases the gas only when a patient inhales and stops the gas supply when the patient exhales. Oxygen can be provided in a small cylinder that can be carried with the patient as large tanks are heavy and are only suitable for stationary use.
Second, regarding liquid oxygen, oxygen is stored as a very cold liquid in a vessel very similar to a thermos. When released, the liquid converts to a gas that a patient may breathe. This storage method takes up less space than the compressed gas cylinder, and the patient may transfer the liquid to a small, portable vessel at home. Liquid oxygen is more expensive than the compressed gas. An oxygen conserving device may be built into the vessel to conserve oxygen.
Third, oxygen concentrators are electrically powered devices that separate oxygen from ambient air, concentrate the oxygen and then store the oxygen. This system does not have to be resupplied, as is the case with compressed gas, and it is not as costly as liquid oxygen. Small, portable systems have been developed that afford even greater mobility. However, compressed oxygen is needed as a backup in the event of a power failure.
Regardless of how the oxygen is stored or supplied, there are three common means for supplying oxygen from the fluid supply to the patient. A nasal cannula is a two-pronged device inserted in the nostrils. The cannula is connected to tubing carrying the oxygen. People who need a high flow of oxygen generally use a mask. Some people who use a nasal cannula during the day prefer a mask at night or when their breathing passages are irritated or congested. Transtracheal oxygen therapy requires the insertion of a small flexible catheter in the trachea or windpipe. The transtracheal catheter is held in place by a necklace. Since transtracheal oxygen bypasses the mouth, nose, and throat, a humidifier is required at flow rates of 1 LPM or greater.
While there are many ways to store the gas and to deliver the gas to the patient, all of the methods face the same limitations. As stated above, the methods use difficult-to-read electronic and mechanical gauges to indicate parameters such as flow rate, percent oxygen delivered and humidity. Therefore, an easier method for quickly and easily determining characteristics or parameters of fluid flow is needed.